Recent studies supported by this grant have begun to fill a major gap in our knowledge regarding neuroinflammation, survival signaling, and protection of the penumbra in experimental stroke. We have found that docosahexaenoic acid (DHA), an omega-3 essential fatty acid-family member, which is selectively enriched and avidly retained in the central nervous system (CNS), upregulates cellular and molecular events when systemically administered that counteract injury and, in turn, exert protection after transient middle cerebral artery occlusion (MCAo). We have discovered that DHA is the precursor of the stereospecific and potent mediator, neuroprotectin D1 (NPD1), and very recently we uncovered during MCAo in the penumbra a novel DHA-derived mediator, which we named neuroprotectin D2 (NPD2). These two docosanoids, through synergizing of their bioactivity, may be critical in driving the protective beneficial effects of DHA. In addition, we have demonstrated that a low molecular weight platelet-activating factor (PAF)-receptor antagonist, LAU-0901 (developed in our laboratory), downregulates neuroinflammation and elicits protection. In both instances, protection has relatively ample windows of post-occlusion, is long-lasting, and correlates with neurobehavioral improvement. Our central hypothesis for the next funding period is that upregulation of DHA survival signaling elicits sustained cellular and behavioral protection of the penumbra after MCAo. We will test this hypothesis in experiments where we drive upregulation of survival signaling by DHA-derived mediators (NPD1 and NPD2) and by neuroinflammatory antagonism (LAU-0901) using MCAo, high resolution magnetic resonance imaging (MRI), primary cell cultures, and LC-PDA-ESI-MS/MS-based mediator lipidomic analysis. We will test the following specific aims: Specific Aim 1 - To test the prediction that the novel DHA-derived mediator, NPD2, which is generated in the penumbra during brain ischemia-reperfusion, elicits neuroprotection; Specific Aim 2 - To test the prediction that NPD1 and NPD2 target survival signaling and pro-inflammatory genes; Specific Aim 3 - To test the prediction that blockage of the PAF receptor elicits penumbra protection after MCAo, downregulating neuroinflammatory signaling. Specific Aim 4 - To test the hypothesis that neuroinflammatory antagonism in combination with docosanoid-mediated survival signaling promotes sustained protection of the penumbra. These findings have the potential to open a new translational avenue for clinical therapies of cerebrovascular diseases.